1. Field of the Invention
The present invention relates to a test beacon for a radar system. More particularly, the present invention relates to a test beacon for a radar system in which one delay line is shared for two separate test beacons and circulators are used to replace separate receiving and transmitting antennas by a single transmitting/receiving antenna.
2. Description of the Related Art
In a typical radar system, a radar controller searches for a target using a search radar, receives data about the target from a tracking radar, and processes the received data to display the result on a screen. To develop the radar controller of a radar system, it is necessary to receive accurate data about a target from the search an d tracking radars. A test beacon for outputting a signal that is phase-shifted and delayed after being reflected by an imaginary moving target is used for the search and tracking radars.
In an earlier test beacon for a radar system, a test beacon for a search radar includes a reception antenna, an isolator, a bandpass filter, a phase shifter, an amplifier, a delay line, another amplifier, another isolator, an attenuator, a directional coupler, still another isolator, and a transmission antenna arranged in that order.
A test beacon for a tracking radar has the same configuration as that of the test beacon for a search radar as noted above, only differing in that parts of a different frequency band are used according to the frequency of the tracking signal used.
However, in the beacon as above, the parts used are duplicated for each of the frequency bands of the search or tracking signals. Also, since parts having the same function are separately installed at the beacons for a search radar and a tracking radar, manufacturing costs become high and the size of the beacon becomes large.
The following patents each discloses features in common with the present invention but do not teach or suggest the specifically recited test beacon for a radar system of the present invention: U.S. Pat. No. 5,138,325 to Koury, entitled Shipboard Sensor Exercise Apparatus, U.S. Pat. No. 4,423,418 to Pearlman, entitled Simulator Of Multiple Electromagnetic Signal Sources Such As In A Radar Signal Field, U.S. Pat. No. 5,442,360 to Maignan et al., entitled Echo Distance-Measuring System With Calibration Apparatus, U.S. Pat. No. 5,339,087 to Minarik, entitled Wavefront Simulator For Evaluating RF Communication Array Signal Processors, U.S. Pat. No. 5,177,488 to Wang et al. entitled Programmable Fiber Optic Delay Line, And Radar Target Simulation System incorporating The Same, and U.S. Pat. No. 5,164,734 to Fredricks et al., entitled Radar Target With Delayed Reply Means.